ROCHESTER — Looking to address problems at the city’s wastewater treatment plant, Waste Management is upgrading its own treatment system on Rochester Neck Road.

Public Works Director Peter Nourse said he hopes with the upgrades will also come a reduction of nitrogen that passes through the city wastewater treatment plant, as about half of the nitrogen that comes through the city plant comes from Waste Management.

By this summer, Waste Management hopes to finish upgrading its treatment plant at the Turnkey Landfill. As part of the upgrade, a reverse osmosis (RO) system will be implemented for the treatment of leachate — the precipitation and melted snow that filters through the landfill waste and collects on the bottom.

After the leachate is pretreated at Waste Management, it travels to the city’s wastewater treatment plant, where it’s treated and then discharged into the Cocheco River.

As part of the final treatment steps, the city’s plant uses UV lights to neutralize any pathogens and contaminants before liquids are discharged into the river. While these UV lights are supposed to operate about 50 percent of the time, Nourse said the lights now operate 100 percent of the time, due to the low transmissivity levels in the liquid that passes through the system.

The higher the levels of transmissivity, the easier it is for light to travel through the liquid, and the easier it is for UV lights to disinfect the water.

“The lower the transmissivity the more stuff you have in there, the more suspended solids, the harder it is to treat,” said Nourse. “We see this being improved with the RO system.”

Studies have shown that the low transmissivity is caused by the leachate from Waste Management, but the specific problem within the leachate remains a mystery.

While the main goal of the RO system is to improve transmissivity at the city wastewater treatment plant, and to make the UV lights not have to operate 100 percent of the time, Nourse said that RO technology also typically results in lower nitrogen levels.

Nourse said that with pilot testing done with the RO system, “It’s promising that it will reduce nitrogen coming to the city.”

“It could be significant, we’re hoping for the best,” said Nourse.

If the implementation of RO means lower amounts of nitrogen coming into the wastewater treatment plant, it would mean the city would have an easier time meeting the upcoming EPA permit for total nitrogen, which is expected to be stringent.

As soon as this year, city officials are anticipating EPA limiting the amount of nitrogen that’s allowed to be discharged from the wastewater plant to 3 milligrams per liter — a level public works officials have called the “limit of technology.” With this permit limit, multimillion dollar upgrades would have to be made to the city’s plant.

Steven Proggi, director of disposal operations for Waste Management, said he’s not certain the new RO system will reduce nitrogen, but he said the Sequencing Batch Reactor (SBR) implemented at the Waste Management plant last year was meant to reduce nitrogen levels, in preparation for the EPA permit.

Nourse, on the other hand, said he doesn’t believe the city saw a reduction of incoming nitrogen with the new SBR system. He said the new system, though, made it so all of the leachate coming from Waste Management is treated. Previously, Waste Management used to send a combination of treated and raw leachate.

Nourse said that with the new RO system, Waste Management is “doing everything they can go get us leachate that we can treat as easily as possible.”

Proggi said that the RO system, which is costing Waste Management millions of dollars, “will make the water lead into the (city) plant very clean, to the point we could probably discharge it directly into the river, but we won’t.”

Nourse noted that the UV lights at the city plant operating at double the normal amount does not cause significant wear and tear on equipment, and does not result in significant extra cost.

He said that Waste Management has been “a proactive partner with the city on this ... they really stepped up to the plate.”

Nourse said that per agreement with Waste Management, the city does not gain any revenue from accepting the company’s leachate, but Waste Management has a limit of how much liquid it’s allowed to send to the wastewater treatment plant.